The causal perturbation expansion of the fermionic projector is performed
with a contour integral method. Different normalization conditions are
analyzed. It is shown that the corresponding light-cone expansions are causal
in the sense that they only involve bounded line integrals. For the resulting
loop diagrams we prove a generalized Furry theorem.Comment: 34 pages, LaTeX, 2 ancillary files, minor improvements (published
version